lib: cache parsed source maps to reduce memory footprint

This also improves performance to map the stack trace when the
`Error.stack` is accessed.

lib/internal/source_map/source_map_cache.js

@@ -3,6 +3,7 @@
 const {
   ArrayPrototypeMap,
   JSONParse,
+  ObjectAssign,
   ObjectKeys,
   ObjectGetOwnPropertyDescriptor,
   ObjectPrototypeHasOwnProperty,
@@ -14,6 +15,9 @@ const {
 
 function ObjectGetValueSafe(obj, key) {
   const desc = ObjectGetOwnPropertyDescriptor(obj, key);
+  if (desc === undefined) {
+    return undefined;
+  }
   return ObjectPrototypeHasOwnProperty(desc, 'value') ? desc.value : undefined;
 }
 
@@ -310,22 +314,25 @@ function findSourceMap(sourceURL) {
   if (!SourceMap) {
     SourceMap = require('internal/source_map/source_map').SourceMap;
   }
-  let sourceMap = esmSourceMapCache.get(sourceURL) ?? generatedSourceMapCache.get(sourceURL);
-  if (sourceMap === undefined) {
+  let entry = esmSourceMapCache.get(sourceURL) ?? generatedSourceMapCache.get(sourceURL);
+  if (entry === undefined) {
     for (const value of getCjsSourceMapCache()) {
       const filename = ObjectGetValueSafe(value, 'filename');
       const cachedSourceURL = ObjectGetValueSafe(value, 'sourceURL');
       if (sourceURL === filename || sourceURL === cachedSourceURL) {
-        sourceMap = {
-          data: ObjectGetValueSafe(value, 'data')
-        };
+        entry = value;
       }
     }
   }
-  if (sourceMap && sourceMap.data) {
-    return new SourceMap(sourceMap.data);
+  if (entry === undefined) {
+    return undefined;
+  }
+  let sourceMap = ObjectGetValueSafe(entry, 'sourceMap');
+  if (sourceMap === undefined) {
+    sourceMap = new SourceMap(ObjectGetValueSafe(entry, 'data'));
+    ObjectAssign(entry, { __proto__: null, sourceMap });
   }
-  return undefined;
+  return sourceMap;
 }
 
 module.exports = {